It is now well established that chronic infiltration of leukocytes into neoplastic tissue potentiates solid tumor development. Many experimental and clinical studies have revealed that tumor-promoting leukocytes regulate essentially all aspects of cancer development. However, the molecular natures of individual leukocyte subtypes associated with developing breast cancers (BCs) are inadequately understood. Our overarching hypothesis is that leukocyte biomarkers in human BC can provide prognostic and predictive information regarding BC outcomes, and that these can also be utilized as platforms for design of new, individualized diagnostic and therapeutic agents. This TMEN proposal is based on our collective goal of generating a comprehensive understanding of the composition and transcriptome characteristics of leukocytes in normal breast tissue as compared to BC. Based on identification of predictive immune-based biomarkers that correlate with BC stage, outcome or response to therapy, we will generate innovative, clinically applicable diagnostic and possibly therapeutic, or combined theragnostic probes for non-invasive in vivo molecular image analysis. Development of these novel and unique reagents will advance our understanding of the tumor microenvironment in BC. As such, we predict that the immune microenvironment In BC can be utilized and exploited to not only predict risk of recurrent disease, and response to therapy, but also to monitor response to therapy and together, these advances will improve outcomes for patients with BC. As such Project 1 will Identify clinically significant leukocyte biomarkers in breast cancer. Project 2 will reveal correlation of outcomes in human breast cancer with leukocyte transcriptomes and novel leukocyte biomarkers; and Project 3 will drive translation of leukocyte biomarkers into clinically applicable diagnostic and therapeutic probes